The field test, launched in late October, also includes participation by Ogilvy North America and Mediaedge:cia.

In the trial, commercial content is being placed in pre- and post-roll positions around "free" on-demand content supplied by Hollywood.com Television and Vehix.com.

Sessions are also created as customers order them, but allow for ad copy updates without the need for costly re-encoding and re-distribution, according to the parties involved.

Before this more flexible method, spots tied to VOD content were spliced in ahead of time, forcing advertisers to commit several weeks in advance and to run more generic messages.

"Charter is now taking dynamic ad insertion to the next phase, which means deploying it as a field pilot focusing on delivering dynamic on-demand advertising built instantly in response to viewers' desires, all based on play lists by viewer sessions," said Todd A. Stewart, Charter's corporate VP of national advertising sales and development, calling the pilot "a breakthrough that entirely changes the landscape of on-demand television advertising."

The companies involved claim the trial marks the largest media market so far to deploy such a service.